Hi there - yes there is a big sleep regression around 4mo, but it sounds like you've already read up on it
And a growth spurt - although at 15w I'm not sure whether it's the one which typically happens at 3mo (13w) or 4mo (17w), either way, at this age I wouldn't worry too much about feeding at night, apart from of course it's tiring, but it could very much still be a genuine need for more milk - I guess with bottles you can keep track to some extent of how much he's getting over 24h, although of course it's harder to say with the bfs. On the positive side, it sounds like he's doing amazingly well with self setting
which may make things much easier as you ride out the 4mo SR, but be aware that 4mo is a tricky time for many, if not most of us, so if you find it so then you're not alone
With the routine issues, it would really help us to help you if you could post a recent day - perhaps the last one which worked well and a recent one which didn't seem to go so well? If he's getting three longish naps and one catnap then that's actually pretty ideal for the 3h easy, don't worry about trying to extend the 4th nap, it will drop off soon enough anyway.
As for the swaddle, the main safety concern is whether he can roll? If so, you will need to wean the swaddle now, but if not, there's no big rush, some LOs keep it until 6mo or beyond, so if you think he didn't respond well to your swaddle weaning attempt then I'd keep it a little longer, until it becomes a problem, either because he's breaking out very often or can roll, as then it becomes a safety issue.
Hope that helps answer some of your questions, I'll try and answer the routine questions once you've posted it
